The present invention relates to a heat-treating apparatus and heat-treating process by using the apparatus for treating such target objects as semiconductor wafers.
In recent years, the continuously increased density of semiconductor integrated circuits has placed severe demands on the characteristics of semiconductor manufacturing equipment.
For example, horizontal type furnaces were the main type of systems for heat-treating semiconductor wafers by such methods as CVD, scattering, oxidation and others. However, when a wafer boat loading semiconductor wafers is loaded in the reaction chamber (tube), reverse flow due to the temperature differential between the interior and exterior of the furnace causes air to enter the reaction tube. This promotes formation of a natural oxidation film on the wafer, and the resulting effect on wafer characteristics has been a problem. For this reason, vertical type heat-treating apparatus have gained attention in recent years.
Another factor has been the recent shift in such demands as DRAM capacity to 4M byte and 16M byte types, leading to still further increase in the density of semiconductor integrated circuits. This necessitates even further suppression of natural oxidation film formation due to air incursion during load or unload, and wafer adhesive components in vertical heat-treatment apparatus as well.
In view of these factors, studies have included construction of the bottom region of the reaction tube of a vertical heat-treatment apparatus as a load lock chamber, in which wafer boat loading and unloading are performed under an inert gas atmosphere.
However, in realizing this type of method, still further refinement is essential regarding the means of wafer transfer between the wafer boat and exterior of the apparatus. Ample consideration is also required with respect to such points as the necessary machinery and equipment space, exchanging the load lock chamber atmosphere, facilitating maintenance, and heat-treatment apparatus start-up time after maintenance.